1. Field of the Invention
This invention relates to a light emitting device which exploits radiation in the p-n junction of a semiconductor. More particularly, it relates to a high-output light emitting device which can make the near field pattern of radiated light uniform.
2. Description of the Prior Art
A semiconductor light emitting device which is used as, e.g., a light source for exciting a solid-state laser and a light source for optical communication employs as its material a compound semiconductor crystal such as Ga.sub.1-x Al.sub.x As. In such a device, light is emitted from a p-n junction when a forward voltage is applied thereto, and this emitted light radiates out from the exterior of the device.
As to such a semiconductor light emitting device, it has been proposed that both positive and negative electrodes are formed on one side of the device, that a compound semiconductor having a wide band gap is arranged on the other side or light emitting side and that the compound semiconductor arranged on the light emitting side is ground into the shape of a dome. It has been known that the light emitting device having this structure exhibits a remarkably high efficiency of producing light.
FIG. 1 shows an example of the light emitting device which has such a structure. Electrodes 6 and 11 are formed on an identical surface. The region of a p-n junction 10 is defined and isolated by a ditch 1.
Heretofore, the ditch 1 has been formed in a manner to reach a first conductivity type (p-type) crystal layer 4. In the light emitting device of such a structure, however, carriers from the outer electrode 11 towards the inner electrode 6 advance at the highest probability along a path close to the ditch 1, such as path 7 indicated by a broken line in FIG. 1. For this reason, the density of current injected into the p-n junction 10 becomes high in a part near the ditch 1, i.e., the peripheral part of the p-n junction and low in a central part.
As a result, the emission of light in the vicinity of the periphery of the p-n junction 10 becomes intenser than in the central part, and the near field pattern of light radiated from the p-n junction 10 does not become uniform in the direction of the plane of the p-n junction. This has often posed problems in optical application, for example, in a precision range finder.